In an axial compressor which is used for a gas turbine engine, a jet engine, or the like, when a stall occurs, failures occur such as a decrease in a pressure ratio, a decrease in an adiabatic efficiency, a decrease in an inflow rate, an adverse flow of an air, or the like. Accordingly, a conventional axial compressor needed to operate with a sufficient margin from an originating point of the stall phenomenon, whereby it was not possible to operate it with its potential performance.
In order to solve these problems, an engine control (active stall control) is proposed which predicts a stall occurrence and avoids the stall from occurring by an actuation. As a stall prediction technique for realizing the active stall control, for example, Patent Document 1 discloses a technique for predicting the stall occurrence by providing a high response pressure sensor on an inner wall surface of a casing in the vicinity of a leading edge of a rotor blade, calculating an autocorrelation value of time-series data of a wall pressure detected by the high response pressure sensor as an index (stall risk index) to evaluate a stall risk, and predict the stall occurrence based on the stall risk index. Patent Document 2 discloses a technique for predicting the stall occurrence by performing frequency demodulation processing with time-series data of parameters (pressure, etc) relative to the compressor, performing a filter processing by using a Kalman filter, calculating a Kalman filter innovation which shows a difference between raw data of the parameters and an estimate value after the filter processing, and using the standard deviation of the Kalman filter innovation as the stall risk index. Patent Document 3 further discloses a technique for calculating the stall risk index by performing a wavelet transformation relative to data showing parameters (pressure etc) relative to the compressor.
U.S. Pat. No. 6,715,984 B2.
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2004-124946
Patent Document 3: Japanese Unexamined Patent Application, First Publication No. 2005-188514